In the related art, in laparoscopic surgery or the like, forceps are used in order to perform various procedures within a body cavity. As one of such forceps, there is known a multi-degree-of-freedom (hereinafter, refer to DOF) forceps that enables bending of a distal end side of a long insertion portion inserted into a body cavity in order to increase the degree of freedom of operations of a treatment portion used to perform a procedure, within a body cavity.
For example, PCT International Publication No. WO2009/088430 discloses a multi-DOF forceps including bending portions at both ends of a long and rigid insertion portion. The two bending portions have a well-known structure in which bending pieces or joint rings are arranged side by side in an axis direction and are connected to each other by an operating member, such as a wire. A treatment portion is connected to one of end portions of the insertion portion and an operating portion is connected to the other. If a user operates a handle or the like of the operating portion to bend the bending portion (second bending portion) closer to the operating portion in a desired direction, the operating member connected to the second bending portion advances and retreats in the axis direction. As a result, the bending portion (first bending portion) distant from the operating portion can be bent in a direction opposite to the second bending portion so as to direct the treatment portion to an intended direction.
When the multi-DOF forceps is used, the insertion portion is inserted into a body cavity from an access port, such as a trocar attached to a patient so as to pass through a body wall, a tissue, or the like. The user moves the treatment portion at the distal end of the insertion portion to a desired position to perform a procedure, using generally three operations including the above-described bending operation, the advance/retreat operation of the insertion portion relative to the access port, and an swinging operation (pivot operation) of the insertion portion having the access port as an operation center.